Isotope separating apparatus



Aug. 9, 1955 H. L. HULL ET AL ISOTOPE SEPARATING APPARATUS Filed Oct. 21, 1946 2 Sheets-Sheet l Aug. 9, 1955 H. L. HULL ET AL ,7 ,186

ISOTOPE SEPARATING APPARATUS Filed 001:. 21, 1946 2 Sheets-Sheet 2 9 7% Flash [2 60:262 J]? Coniral Circuit Curran? Responsive Device INVENTORS! Maw United States Patent Office Patented Aug. 9, 1955 isororr. SEPARATING APPARATUS Harvard L. Hull and Stephen 1%. MacNeille, Oak Ridge, Tenn, assignors, by mesne assignments, to the United States of America as represented by the United States tomic Energy Commission Application October 21, 1946, Serial No. 704,574

Claims, (Cl. 250-419) This invention relates generally to isotope separating apparatus and is particularly directed to improvements in apparatus of this type which is commonly referred to as a calutron, wherein the material, the isotopes of which it is desired to separate, is initially vaporized by the controlled application of heat.

In such apparatus, after initial vaporization of the charge material, the vapor is permitted to enter an elongated ionization chamber where it is subjected to an electric arc in order to disassociate and ionize the atoms of this vapor. maintained at an appropriate temperature such as to prevent condensation of the vapor by means of an external heating coil and associated thermostat and control circuit. The positive ions are then withdrawn through an elongated slit in the top of the ionization chamber and at the same time are projected in the form of a high velocity ribbon like beam into the interior of the calutron unit, these actions being accomplished by means of one or more slotted accelerating electrodes disposed adjacent the ionization chamber and maintained at a high negative potential with respect thereto. Due to the effect of the transverse magnetic field, the ion beam is then bent into the form of an arc and is split into component isotope beams which may be separately collected at a receiver located at the 180 point in their travel.

In the proper operation of such apparatus, it is important that the flow of vapor to the ionization chamber be at a rate which the ionizing arc is just able to handle eifectively. Too great a flow of vapor is wasteful of charge material in that the percentage of the vapor which is actually ionized is small. Too great a flow is also detrimental by reason of the fact that a large number of un-ionized particles spew out of the slit in the top of the ionization chamber and deposit on the edges of this slit and on other portions of the calutron, thus changing efiective dimensions of critical parts and generally interfering with normal operations. On the other hand, an insufiicient flow of vapor to the ionization chamber is obviously inefiicient.

The present inventors, having noted that a change in the rate of flow of vapor to the ionization chamber is closely followed by a corresponding change in the drain current to the first accelerating electrode, that is, the number of ions which impinge upon, and are deionized by, this first electrode, have conceived that the supply of This ionization chamber is automatically 5. '1

justing the rate of vaporization of the charge material for optimum calutron operation, said apparatus including an internal radiant heater positioned closely adjacent the charge material and a control circuit for energizing this heater in response to variations in the drain current to the first accelerating electrode.

Other objects and advantages of the invention will become apparent from the description and accompanying drawings wherein one embodiment of the invention is illustrated.

In the drawings,

Fig. 1 is a diagrammatic view of an isotope separator of the type which employs an ion source in which the control feature of the present invention may be practiced.

Fig. 2 is a diagrammatic sectional view taken along line 22 of Fig. 1.

Fig. 3 is a view of the control arrangement of my invention applied to the ion producing source which is used in the system of Fig. 1.

Referring to Fig. l of the drawings, there is shown diagrammatically an apparatus for isotope separation, the apparatus being of the type which includes ion generating means wherein a solid material is volatilized by the application of heat. Our invention is particularly adapted to the control of the application of the heat for volatilizing the material, so as to desirably regulate the amount of vapor present for ionization. The apparatus of Fig. 1 is of the type disclosed in greater detail in the application of Ernest 0. Lawrence, Ser. No. 557,784, filed October 9, 1944. The apparatus of Fig. 1 includes a tank .10, the interior of which is evacuated to a relatively high degree of vacuum as will be presently described. The tank is rectangular in cross section and one side is closed by a relatively heavy face plate 11 which is attachable to the tank by means of screw clamps 12 and 13, there being provided suitable bearing surfaces on face plate 11 and on the tank 10 so that when the face plate 11 is clamped into position, the tank 10 is attached to and carried by the face plate 11 as will be presently explained.

The tank 1i) has windows 14, 15, 16 and 17 so as to make it possible to watch operations within the tank, and it has a large discharge outlet 20 through which the air and moisture within the tank are evacuated. The discharge outlet 20 is connected to a diffusion pump or pumps 21 by pipe 22 and the diffusion pump is connected to a mechanical pump or pumps 23 by pipe 24. The mechanical pump 23 may be a Kinney pump for example. This pump is of the rotary type.

The tank 10 is disposed between laminated iron cores or poles 27, as shown in cross section in Fig. 2, and wound around these pole pieces are electrical windings 28, the windings being disposed within tanks or housings 29, the housing 29 being shown in cross section in Fig. l. The windings 28 are energized with electric current so that a relatively intense magnetic field is produced which is in a direction transverse to the tank 10, that is, a horizontal direction looking at Fig. 2 and in a direction perpendicular to the paper looking at Fig. 1. A cooling medium such as cooled oil or the like is circulated through the housings 29 for the purpose of cooling the coils therein.

Within the tank 16 is a liner structure in the form of an arcuate conduit which forms a passageway for a beam or beams of ions generated at the lower end of the liner and received in a receiver at the upper end of the liner. The liner 35 is carried by the face plate 11 by means of supporting structure designated by the numerals 36 and 37 and the brace member indicated by 38 and is supported from insulators $2, 33, and 34. Within the lower right hand corner of the tank 10 there are a pair of castings 40 and 41 which form containers within which a 3 material to be ionized is volatized. These castings are suitably supported within the tank and since they are identical and the structure and controls associated with each one are identical, only one will be described in de-,

tail. Our invention is particularly concerned with the manner of control of the volatilizing of the material within the containers 40 and 41; the automatic control apparatus for the heaters associated with the containers 40 and 41 is shown in detail in Fig. 3.

The casting 40 comprises a lower portion 31 and a smaller upper portion 42, the two portions being connected by a converging throat as shown. Within the portion 31 is a container or bottle 43 which is removable and in which the charge material itself is placed, that is, the charge of material to .be ionized. Within the bottle 43 is a flash or radiant type heater 44 which may be the well known Calrod type of heater consisting of an electrical resistance element wound upon a suitable insulating member. One end of the heating element is connected to a source of power and the other end is grounded as will be described, by being connected to the casting 40 or the like. The vaporized material passes from portion 31 into portion 42 through a chimney 45, the'vaporized material passing up and over a baffie member 46 adjacent the entrtance end of the chimney 45. At the left end of the portion 42, there is a longitudinal slit 50 through which the vaporized material passes. Disposed at one end of this slit is a cathode 51 across the terminals of which a suitable voltage is impressed when the apparatus is in operation. The function of the cathode 51 in operation is to emit a stream of electrons into and along the slit 50 for the purpose of ionizing the vapor passing therethrough as will be presently described. Numeral 52 designates electric heating elements associated with the portion 42 and to which electrical energy is supplied frorna voltage source V5, one end of the heating elements being grounded by being connected to the casting 40 for example. Numeral 53 designates a well in a sidewall of the portion 42 and in which a thermocouple is located, the thermocouple being for the purpose of controlling the supply of heat to the heating elements by controlling the voltage V through an external. automatic temperature control system, not shown.

To the left of the casting 40, that is above it, is an electrode member 56 which may preferably be made of carbon and which has therein a slit parallel to the slit 50so that the vapor emitted through the slit 50 can also pass through the slit in electrode 56. The electrode 56 constitutes an accelerating electrode for positive ions emerging from the slit 50 and this electrode is maintained at a relatively'high negative potential as will presently be described. V

The ions accelerated by the electrode 56 pass to the left, that is upwardly, through another slit in a member 57 forming a throat, and the slit in this throat is also in'the form of an electrode 58 made of carbon and it is maintained at a relatively high negative potential somewhat lower than the potential of electrode 56. Positive ions after passing through the throat 57 pass into the a liner structure 35 and then travel in arcs of a circle around through the liner to the receiving structure at the opposite end of the liner; the positive ions move in arcs of a circle in this manner under the influence of the magnetic field previously described and theradii of the arcs depends upon the mass-charge properties of the ions.

There are two identical receiving chambers at the upper end of the liner structure 35, one of them being designated by the numeral 60. The receiving chamber 60 is in the form of a box having a shape which in cross section is as shown in Fig. 1. The receiver 69 may be adjusted laterally relative to the face plate 11 by stem 61 operating through linkages 62, and it may be adjusted in and out relative to the face plate. by means of stem 63, the

stems passing through suitable sealing devices 64 and 65 respectively associated with the face plate 11. The receiver 60 has pockets 71 and 72 therein which are so located as to receive certain components of the beam of ions which travels around through the liner 35, diiferent components of the beam, that is, particles-having different mass-charge properties travelling in circles of different radii as described above. Within the pockets 71 and 72 are electrodes 73 and 74 respectively which are maintained at a certain potential which will presently be referred to.

The face plate 11 is grounded, as shown, as are the castings 40 and 41, and theliner and the electrode 58 forming part of'throat 57 are maintained at a relatively high negative potential V1 by conductor 75 which is led into the interior of the tank through a conduit 76 which extends through the face plate through a scaling insulator bushing 77. The electrode 56 is maintained at a higher negative potential V1+V2 by means of a conductor 78 which is also led into the tank through the bushing 77 and the conduit 76. The electrodes 73 and 74 and the receivers 60 are maintained at the potential V1 by means of conductors 79, 80, and 81. The conductors leading to the electrodes in the receiver 60 extend through a conduit and bushing similar to those for the conductors 75 and 78 as shown. A potential V3 is across the terminals of the cathode 51 and a potential V4 is impressed between the negative terminal of cathode 51 and ground, that is the casting 40. This latter potential sustains the are which is struck within slit 50 during operation.

Summarizing the operation of the apparatus as so far described, the charge material in the bottle 43 is vaporized by the radiant heater 44 and the vapor passes up into the upper portion 42 of the casting where it is maintained in vapor state by the heating elements 52. The vapor passes up through the slit where it is ionized by the stream of electrons from the cathode 51, an are being formed in the slit 50 under the influence of voltage V4. Positive ions are attracted from the region of the slit by electrode 56, which is maintained at a negative high potential, and under the influence of electrode 58, the ions pass into the liner structure 35 and thence travel in arcs of a circle around to the receiver 60, the radii of the arcs depending upon the mass-charge properties of the ionized particles. The receiver is adjusted as described so that the desired isotopes of the,

ionized material is received in the collector pockets.

With reference to the structure so far described, it will be understood that those elements which are maintained at high potentials are suitably insulated from other elements at lower or ground potential. Also various of the parts within the tank 10 may be cooled as desired by a suitable fluid cooling system and shielding may be provided at appropriate points to protect the mechanism from becoming coated as a result of being contacted by the vapor from the charge bottle and for protection from deterioration which may necessarily result from the process.

Referring now to Fig. 3 of the drawing, this figure shows the automatic controls for the radiant heaters 44 associated with. the castings 40 and 41 whereby the volatilization of the material to be ionized is controlled. During the process some of the positive ions are collected by the electrode 56 and lose their charge so that there is a small current flow through the circuit of this electrode. In order that the process proceed desirably and efliciently, the quantity of vapor present for ionization must be accurately controlled and the amount of current in the circuit of electrode 56, that is, drain current is an accurate indication of the amount of vapor present for ionization. The objective of our invention as stated above is to provide a control circuit'whereby the volatilization of the material to be ionized may be appropriately controlled in response to the drain current through the circuit of electrode 56.

The voltage which is impressed on electrode 58 is supplied from a regulated kv. supply V1 indicated diagrammatically at 93, the positive of this supply being connected to ground as shown. The potential impressed on electrode 56 is supplied from the supply 93 and a second 15 kv. supply V2, schematically indicated at 94, so that the voltage on electrode 56 is kv. Connected between the voltage supplies V1 and V2 is a current responsive device, indicated schematically at 90. Device may be any type of conventional apparatus adapted to derive an electrical signal proportional to the drain current to electrode 56 and to transmit this signal to the flash heater control circuit indicated schematically at 91 by way of leads 92. Flash heater control circuit 91 is adapted to control the energization or non-energization of winding 117 of control relay 118 according to whether the input signal received on input leads 92 is above or below a predetermined value corresponding to the setting of drain current control knob 97. Another control knob 98 controls the sensitivity of control circuit 91. A regulated source of alternating current, indicated at 95, supplies the operating power for control circuit 91. The details of current responsive device 90 and flash heater control circuit 91 may be as described in U. S. application Serial No. 573,615 for Electrical Control Circuit, filed January 19, 1945, in the name of Hugh G. Neil, although many other suitable types of such apparatus could be employed.

The position of the contacts of relay 118 controls the supply of power from an alternating source 96 by way of a transformer 119 to two auto-transformers 120 and 121 connected in parallel, these transformers being of the type known commercially as variacs. The autotransformer 121 controls the supply of power to the flash heater 44 within casting 40, and the auto-transformer 120 controls the supply of power to the corresponding heater in the casting 41. The slider of auto-transformer 120 controls the supply of power to the corresponding heater in the casting 41. The slider of auto-transformer 121 connects by wire 125 to the electric heating element 44, the other end of this element being grounded by being connected to the casting 40 as described above. One terminal of the auto-transformers is also grounded as shown in Fig. 3.

In the operation of the circuit arrangement shown in Fig. 3, a signal is transmitted from current responsive device 90 to flash heater control circuit 91, which signal corresponds to the drain current to electrode 56, which in turn corresponds to the rate of vaporization of the charge material within castings 40 and 41. If this control signal is greater than the setting of control knob 97, which setting corresponds to the desired rate of vaporization, the flash heater control circuit 91 operates to deenergize relay 118 thus opening its contacts and interrupting the power circuit to the flash heaters 44. On the other hand, if the rate of vaporization of the charge material is too low, the relay 118 is energized which in turn effects the energization of flash heaters 44. Flash heaters 44 radiate directly upon the charge material so that the rate of vaporization of the charge material changes almost instantaneously in response to energization or deenergization of these heaters.

The embodiment disclosed herein is a preferred form of our invention, and it is intended that it be interpreted in an illustrative rather than a limiting sense. It is intended that the scope of the invention be determined only in accordance with the claims appended hereto.

We claim:

1. In an isotope separator, apparatus for projecting a beam of positive ions of the material the isotopes of which are to be separated, comprising, in combination, a container for said material in its solid state, means associated with said container for radiating heat onto said fit) material for vaporizing the same, an ionization chamber communicating with said container for receiving said vapor, means for ionizing said vapor within said ionization chamber, said chamber being apertured at one end to allow ions to escape therefrom in the form of a beam, an accelerating electrode system, including two apertured electrodes sequentially spaced adjacent said chamber, for withdrawing a beam of positive ions from said chamber and through the apertures in said electrodes, and means for controlling said heat radiating means in response to the drain current to the first of said electrodes.

2. In an isotope separator, apparatus for projecting a beam of positive ions of the material the isotopes of l which are to be separated, comprising, in combination,

a container for said material in its solid state, radiant heating means disposed within said container and closely adjacent said material for vaporizing said material, an ionization chamber communicating with said containcr for receiving said vapor, means for ionizing said vapor within said chamber, a said chamber being apertured at one end to allow ions to escape therefrom in the form of a beam, an accelerating electrode system, including two apertured electrodes sequentially spaced adjacent said chamber, for Withdrawing a beam of positive ions from said chamber and through the apertures in said electrodes, and means for controlling said radiant heating means in response to the drain current to the first of said electrodes.

3. In an isotope separator, apparatus for projecting a beam of positive ions of the material the isotopes of which are to be separated, comprising, in combination, a container for said material in its solid state, means associated with said container for radiating heat onto said material for vaporizing the same, an ionization chamber communicating with said container for receiving said vapor, means for ionizing said vapor within said ionization chamber, said chamber being apertured at one end to allow ions to escape therefrom in the form of a beam, a pair of spaced apertured accelerating electrodes for withdrawing a beam of positive ions from said chamber and through the apertures in said electrodes, and means for controlling said heat radiating means in response to the drain current to the first of said electrodes.

4. In an isotope separator, apparatus for projecting a beam of positive ions of the material the isotopes of which are to be separated, comprising, in combination, a container for said material in its solid state, radiant heating means disposed within said container and closely adjacent said material for vaporizing 'said material, an ionization chamber communicating with said container for receiving said vapor, means for ionizing said vapor within said ionization chamber, said chamber being apertured at one end to allow ions to escape therefrom in the form of a beam, a pair of spaced apertured accelerating electrodes for withdrawing a beam of positive ions from said chamber and through the apertures in said electrodes, and means for controlling said radiant heating means in response to the drain current to the first of said electrodes.

5. In an isotope separator, apparatus for projecting a beam of positive ions of the material the isotopes of which are to be separated, comprising, in combination, a container for said material in its solid state, radiant heating means disposed within said container and closely adjacent the material for vaporizing said material, an ionization chamber communicating with said container for receiving said vapor, means for ionizing said vapor within said chamber, said chamber being apertured at one end to allow ions to escape therefrom in the form of a beam, an accelerating electrode system for withdrawing a beam of positive ions from said chamber, said accelerating system comprising first and second electrodes arranged successively adjacent said chamber,

said electrodes each having an aperture aligned with the aperture in said chamber for permitting passage of the ion beam through said electrodes, means for maintaining said first electrode at a negative potential with respect to said chamber, means for maintaining said second electrode at a potential which is negative with respect tosaid chamber but'positive with respect to said first electrode, and means for controlling said radiant heating means in response to the drainv current to said first electrode.

References Cited in the file of this patent UNITED STATES PATENTS Atherton Feb. 14, 1922 'Kearsley Sept. 4, 1928 Morrison June 5, 1934 Bleakney Nov. 12, 1940 Philpott Nov. 11, 1941 

1. IN AN ISOTOPE SEPARATOR, APPARATUS FOR PROJECTING A BEAM OF POSITIVE IONS OF THE MATERIAL THE ISOTOPES OF WHICH ARE TO BE SEPARATED, COMPRISING, IN COMBINATION, A CONTAINER FOR SAID MATERIAL IN ITS SOLID STATE, MEANS ASSOCIATED WITH SAID CONTAINER FOR RADIATING HEAT ONTO SAID MATERIAL FOR VAPORIZING THE SAME, AN IONIZATION CHAMBER COMMUNICATING WITH SAID CONTAINER FOR RECEIVING SAID VAPOR, MEANS FOR IONIZING SAID VAPOR WITHIN SAID IONIZATION CHAMBER, SAID CHAMBER BEING APERTURED AT ONE END TO ALLOW IONS TO ESCAPE THEREFROM IN THE FORM OF A BEAM, AN ACCELERATING ELECTRODE SYSTEM, INCLUDING TWO APERTURED ELECTRODES SEQUENTIALLY SPACED ADJACENT SAID CHAMBER, FOR WITHDRAWING A BEAM OF POSITIVE IONS FROM SAID CHAMBER AND THROUGH THE APERTURES IN SAID ELECTRODES, AND MEANS FOR CONTROLLING SAID HEAT RADIATING MEANS IN REPSONSE TO THE DRAIN CURRENT TO THE FIRST OF SAID ELECTRODES. 